Interpolating mesh and boundary mesh should not require extrapolation

Consider this:

$ cat test.py 
#!/usr/bin/env python

import dolfin
from dolfin import Mesh, BoundaryMesh, FunctionSpace, Function

print(dolfin.__version__)

#dolfin.parameters['allow_extrapolation'] = True
dolfin.parameters["linear_algebra_backend"] = "PETSc"
dolfin.set_log_level(dolfin.WARNING)

mesh = Mesh('mesh.xml.gz')
bmesh = BoundaryMesh(mesh, 'exterior')

V_DG = FunctionSpace(mesh, 'DG', 0)
Vb_DG = FunctionSpace(bmesh, 'DG', 0)

dpsi_dn_b = Function(Vb_DG)
dpsi_dn = Function(V_DG)
dpsi_dn_b.interpolate(dpsi_dn)

$ python test.py 
1.3.0
Traceback (most recent call last):
  File "test.py", line 20, in <module>
    dpsi_dn_b.interpolate(dpsi_dn)
RuntimeError: 

*** -------------------------------------------------------------------------
*** DOLFIN encountered an error. If you are not able to resolve this issue
*** using the information listed below, you can ask for help at
***
***     fenics@fenicsproject.org
***
*** Remember to include the error message listed below and, if possible,
*** include a *minimal* running example to reproduce the error.
***
*** -------------------------------------------------------------------------
*** Error:   Unable to evaluate function at point.
*** Reason:  The point is not inside the domain. Consider setting "allow_extrapolation" to allow extrapolation.
*** Where:   This error was encountered inside Function.cpp.
*** Process: 0
*** 
*** DOLFIN version: 1.3.0
*** Git changeset:  
*** -------------------------------------------------------------------------

It seems to me that setting allow_extrapolation really should not be required - the vertices of bmesh coincide with those of mesh.

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